// alert("hello world"); // 弹出提示框

console.log("hello world"); // 输出到控制台

console.log('子曰："学而不思则罔，思而不学则殆。"');

console.log("子曰：\"学\而\不\思\则\罔\, \思\而\不\学\则\殆\。\"");


// 2. 变量
// 2.1 声明变量
// var 变量名 = 值;
var n = "jack";
var age = 18;
var weight = 60.5;
var isMan = true;

// symbol
var s = Symbol("hello");
var s1 = Symbol("hello");

console.log(typeof n);
console.log(typeof (age));
console.log(typeof weight);
console.log(typeof isMan);
console.log(typeof null);
console.log(typeof undefined);

console.log(typeof s);
console.log(typeof s1);
console.log(s == s1);


// 变量可以只声明不赋值或者直接赋值

var a;

console.log(a);

// 全局变量
b = 1;
console.log(b);

b = "hello";


b = true;

var name = "jack";
b = `hello ${name}`;
console.log(b);

